Recently it has been shown that 3T3-L1 fibroblasts growing in culture can convert into adipose cells. This conversion is a type of differentiation which occurs after the cells form a monlayer and stop growing. The conversion occurs slowly on treatment with serum (30%) on insulin (1 microgram/ml) for three weeks. Insulin most likey does not trigger differentiation but is involved in stimulating triglyceride synthesis in the adipose cells. Prostaglandin F2 alpha and 1-methyl-3-isobutyl xanthine trigger the differentiation process by rapidly and irreversibly programming the fibroblasts to differentiate into adipose cells within 8 days. The proposed research involves further studies of this interesting phenomenon in the hopes of gaining insight at the molecular level of the differentiation process. To determine if the triggering of differentiation is a general phenomenon, a number of cell types will be treated to determine if adipocyte conversion occurs. Hormonal responsiveness will be investigated using epinephrine, glucagon and ACTH in any cells that exhibit the conversion into adipocytes. Triglyceride formation is measured by Oil-Red-O staining and radioactive labeling of lipids. Prostaglandin binding, subcellular distribution, specificity and the effect of indomethacin on the conversion process will be studied. The role of the cyclic nucleotides in the triggering of differentiation will also be investigated with emphasis on the enzymes involved in cyclic nucleotide metabolism.